The invention relates to a method of generating colour matte signals comprising the steps of: inputting hue, saturation, and luminance values; and calculating red (R), green (G), and blue (B) colour component values from the hue, saturation and luminance values. The invention further relates to a colour matte generator having variable luminance, saturation, and hue controls comprising means for calculating red (R), green (G), and blue (B) colour components from the luminance, saturation, and hue values.
Colour matte generators have conventionally been used in television studio equipment such as special effects generators for providing background or foreground colour within a television picture particularly where a squeeze or compression of the picture has been carried out, the colour matte being used to fill up the rest (the black part) of the picture. Existing colour matte generators suffer from the disadvantages of either generating illegal colours, i.e. where the red, green or blue components take illegal values either negative or greater than the maximum permissible value, or restrict the range of available colours to ensure that illegal values are not generated.